1. Field of the Invention
This invention relates to control devices for air conditioners, and more particularly to devices which are capable of providing a comfortable environment adapted to the preference of individual users.
2. Description of the Prior Art
In small self-contained air conditioners, both the cooling and warming of air are effected by means of a heat pump driven by a compressor. In the cooling operation, the air cooled by the expansion of the refrigerant gas in the evaporator is delivered to the room; in the heating or warming operation, the direction of circulation of the refrigerant is changed over, and the air warmed by the condensation of the refrigerant is delivered to the room. These types of air conditioners are often installed to condition the air of a single room; hence, it is preferable to control them according to the varying preference of individual users. However, the control of such air conditioners is usually effected according to a fixed standard which can not be adapted to individual preferences or conditions of users.
FIGS. 1 and 2 show circuit diagrams of an air conditioner (a temperature and humidity control device) and its control circuit disclosed in the Japanese laid-open patent application No. 56-18236. As shown in FIG. 1, the circuitry of the temperature and humidity control device THC comprises a compressor CM, motors for indoor and outdoor fans FM.sub.1 and FM.sub.2, a valve SV.sub.1 for dehumidifying operation cycle, and a valve SV.sub.2 for a cooling operation cycle. When the cooling operaton is performed, the switch RY-1-S (interlocked to the relay RY-1 shown in FIG. 2) is made to the side of the contact point NC; when, on the other hand, the slightly warming dehumidifying operation is performed, it is made to the side of the contact point NO. The relay RY-1 itself is operated by the control circuit shown in FIG. 2.
The control circuit of FIG. 2 comprises a temperature detecting circuit, a humidity detecting circuit, and a circuit for driving the relay RY-1 according to the detected temperature and humidity. In the following, these circuits are described in the above order.
The temperature detecting circuit in the control circuit of FIG. 2 comprises a temperature detector TD, a Zener diode ZD.sub.1 for giving a reference voltage v.sub.2 corresponding to a reference temperature, an operational amplifier IC1 for subtracting the reference voltage v.sub.2 given by the Zener diode ZD1 from the detected voltage v.sub.1 outputted from the temperature detector TD. Since the resistance of the temperature detector TD has a negative temperature characteristic and a constant voltage +V.sub.1 is applied across the voltage divider consisting of the temperature detector TD and the resistor R.sub.1, the voltage v.sub.1 becomes increasingly higher as the temperarure rises. The detected voltage v.sub.1 is applied to the noninverting input terminal of the operational amplifier IC.sub.1 through the resistor R.sub.4. On the other hand, the reference voltage v.sub.2 is applied to the inverting input terminal thereof through the resistor R.sub.3. Thus, the output voltage v.sub.3 of the operational amplifier IC.sub.1 having a feedback resistor R.sub.5 across the output and the inverting input terminal thereof is expressed by the following equation: ##EQU1## Consequently, the output voltage v.sub.3 of the operational amplifier IC1 is proportional to the voltage v.sub.1.
The humidity detecting circuit, on the other hand, comprises an oscillator circuit OSC, a humidity detector HD, and AC/DC converter circuit LEC for converting the detected AC voltage v.sub.4 of the humidity detector HD into a DC voltage v.sub.5. The oscillator circuit OSC is provided for the humidity detector HD, since the humidity detector HD of FIG. 2 is operated by an AC voltage; in cases where it is operated by a DC voltage, the direct voltage +V.sub.1 may be applied thereto. The voltage v.sub.4 detecting the humidity appears at the junction between the detector HD and the resistor R.sub.6. Since the humidity detector HD has a negative resistance characteristic, the detected voltage v.sub.4 becomes increasingly higher as the humidity rises. The AC voltage v.sub.4 is converted into a DC voltage v.sub.5 by the AC/DC converter circuit LEC.
The output voltages v.sub.3 and v.sub.5 of the temperature and humidity detecting circuits are applied across the voltage divider consisting of the serially connected resistors R.sub.7 and R.sub.8, thereby obtaining at the junction between the resistors a composite voltage v.sub.6 : EQU v.sub.6 =(v.sub.3 .multidot.R.sub.8 +v.sub.5 .multidot.R.sub.7)/(R.sub.7 +R.sub.8), (2)
which is applied to the negative input terminal of a comparator circuit IC.sub.2. A variable resistor VR.sub.1 connected in series with a resistor R.sub.9 gives a reference voltage v.sub.7, which is applied to the positive input terminal of the comparator circuit IC.sub.2 through a resistor R.sub.10. A feedback loop consisting of a resistor R.sub.11 and a diode D.sub.1 is coupled between the output and the positive input terminal of the comparator circuit IC.sub.2, so that the output v.sub.8 thereof has a hysteresis characteristic. Namely, when the diode D.sub.1 is in the non-conducting state, the reference voltage for the voltage v.sub.6 given by equation (2) takes a first value Vref.sub.1 corresponding to the comfort line Pa-Pa' shown in FIG. 3: the transistor Q.sub.1, the base of which is coupled to the output of the comparator circuit IC.sub.2 through a resistor R.sub.12, is turned off at the time when the voltage v.sub.6 given by equation (2) rises to a first reference voltage Vref.sub.1 corressponding to the comfort line Pa-Pa' shown in FIG. 3. When, on the other hand, the diode D.sub.1 is in the conducting state, the reference voltage for the voltage v.sub.6 falls to a second level Vref.sub.2 corresponding to the comfort line Pb-Pb' shown in FIG. 3; namely, the transistor Q.sub.1 is turned on at the time when the voltage v.sub.6 falls to the second reference voltage Vref.sub.2. The relay RY-1 is coupled in series with the transistor Q.sub.1, so that the switch RY-1-S is changed over between the contacts NO and NC shown in FIG. 1 as the transistor Q.sub.1 is turned on and off. Thus, the temperature and the humidity are controlled within a region between the comfort lines Pa-Pa' and Pb-Pb' as described below.
In FIG. 3, lines Pa-Pa' and Pb-Pb', the upper and lower limit comfort lines plotted in the T-H (temperature-humidity) plane, define therebetween an allowable variation region of temperature and humidity within which they are controlled. The control of the temperature and humidity control device THC of FIG. 1 by the control circuit of FIG. 2 takes two different modes according to the initial position of the point representing the temperature and humidity in the T-H plane: a first mode is taken when the initial point falls in the region A which is situated above and to the right of the comfort line Pa-Pa'; a second mode is taken when it falls in the region B which is situated below and to the left of the comfort line Pb-Pb'. The initial point at which the device THC begins to be operated falls in the region A when the load to cooling operation is large in the room which is air-conditioned; it falls in the region B when the load is small. The load characteristics of a room depends on such factors as the structure, dimension, heat insulating property thereof, or the existance of heat sources (including human beings). The load of the room is large to the cooling operation when the temperature of the room tends to rise rapidly by its nature; conversely, it is small when it tends to remain low. In the following, the two modes of control operation of the device THC is described in greater detail.
The first control mode is effected along the solid line I of FIG. 3 as follows. When the initial point 0 in the T-H plane falls in the region A as shown in FIG. 3, the cooling operation is effected first from point 0 to reduce the temperature. At the time when the point in the T-H plane reaches point 1 on the lower limit comfort line Pb-Pb', the operation is switched to the slightly warming dehumidifying operation to reduce the humidity, whereby the temperature of the room rises by its natural tendency. Thus, the point in the T-H plane moves from point 1 to point 2 on the upper limit comfort line Pa-Pa'. When the point in the T-H plane reaches at point 2, the operation is again switched to the cooling mode and the point in the T-H plane turns to point 3 on the lower limit comfort line Pb-Pb'. Thus the point in the T-H plane moves in a zigzag line 1, 2, 3, 4, --- , 5 in FIG. 3. In this way, by alternating the cooling and the slightly warming dehumidifying operation in the allowable variation region between the upper and lower limit comfort lines Pa-Pa' and Pb-Pb', the temperature and humidity of the room are controlled to a comfortable condition at which these two values are balanced.
The second control mode is effected along the dotted line II of FIG. 3 as follows. When the initial point 0' falls in the region B in the T-H plane, the slightly warming dehumidifying operation is effected first from point 0'. At the time when the point 1' on the upper limit comfort line Pa-Pa' is reached, the operation is switched to the cooling operation. Thus, the point in the T-H plane moves from point 1' to point 2' on the lower limit comfort line Pa-Pa', at which the operation is again switched to the dehumidifying mode and the point in the T-H plane turns to point 3' on the upper limit comfort line Pa-Pa'. Thus the point in the T-H plane moves in a zigzag line 1', 2', 3', 4', --- , 5' in FIG. 3. In this way, by alternating the slightly warming dehumidifying operation and the cooling operation in the allowable variation region between the upper and lower limit comfort lines Pa-Pa' and Pb-Pb', the temperature and humidity of the room are controlled to a comfortable condition at which these two values are balanced.
The above described air conditioner (temperature and humidity control device) is controlled automatically according to a fixed standard. However, the condition which is felt comfortable varies according to the user's physiology, state of health, amount of physical excercise being performed, or amount of apparel. Thus, the above air conditioner has the disadvantage that the control standard cannot be adapted to the varying preferences and conditions of individual users. In view of this, the Japanese laid-open patent application No. 62-91735 discloses an air conditioner which is capable of modifying the control standard according to the preference and condition of individual users.
FIGS. 4 and 5 show the organization of the control device of such an air conditioner. An operation panel P shown in detail in FIG. 5 is provided with hotness sensation switches 1, operation mode selecting switch 2, an operation switch 3, and fan speed change-over switch 4. The hotness sensation switches 1 comprise a "too hot" switch 1a and a "too cold" switch 1b; the "too hot" switch 1a and "too cold" switch 1b are used when the user feels that it is too hot or too cold. The operation mode selecting switch 2 is for selecting the operation mode, i.e., the heating or the cooling mode, and the operation switch 3 is for starting the cooling or the heating operation. The fan speed change-over switch 4 is used for selecting the fan speed. A thermistor 5a detects the room temperature, and an A/D converter 5b converts the analog output of the thermistor 5a into a digital signal. A microcomputer 6 comprises an input circuit 6a, a CPU (central processing unit) 6b, a memory 6c, and an output circuit 6d. The microcomputer 6 compares the detected room temperature with the setting temperature, and controls the turning on and off of the compressor 7 according to the selected operation mode. Further, it sets the setting temperature two degrees lower than the room temperature when the "too hot" switch is turned on; conversely, it sets the setting temperature two degrees higher when the "too cold" switch is turned on. In addition, the microcomputer 6 controls the rotational speed of the fan 8 according to the input through the fan speed change-over switch 4.
FIG. 6 is a flowchart showing the steps followed by the microcomputer 6 in controlling the compressor 7 and the fan 8 during the heating operation. First, the heating mode is selected by means of the operation mode selecting switch 2. Next, when the operation switch 3 is turned on, the initial setting temperature is set at step 101, and the room temperature detected by the thermistor 5 is taken in at step 102. Further, the setting temperature is compared with the detected room temperature by the microcomputer 6 at step 103; when the setting temperature is higher than the room temperature, the compressor 11 is turned on at step 104; when, on the other hand, the setting temperature is lower than the room temperature, the compressor 11 is turned off at step 105. At the next step 106, judgement is made as to the fan speed input through the switch 4; when the switch 4 is at the "fast" position, the fan 8 is set at fast speed at step 107; on the other hand, when the switch 4 is at the "slow" position, the fan 4 is set at the slow speed at step 108. At step 109, judgement is made whether or not there is an input through the hotness sensation switches 1; when the judgement is negative, the control procedure returns to step 102; when, on the other hand, the judgement is affirmative, judgement is further made at the next step 110 as to which one of the two switches, the "too hot" switch 1a or the "too cold" switch 1b, is turned on. When the "too hot" switch 1a is turned on, the setting temperature is set two degrees lower than the current room temperature at step 111; when, on the other hand, the "too cold" switch 1b is turned on, the setting temperature is set two degrees higher than the current room temperature at step 112. Thereafter, the steps 102 through 112 are repeated.
The steps followed in the cooling operation is substantially the same as those of the heating operation described above: First, the cooling mode is selected by means of the operation mode selecting switch 2, and the steps corresponding to the steps 101 through 112 are followed. However, at the steps corresponding to steps 104 and 105 in the heating operation, the compressor 7 is turned off when the setting temperature is higher than the room temperature, and turned on when the setting temperature is lower than the room temperature.
The above air conditioner is capable of adapting the control standard to the individual preference of users. However, it has the following disadvantage. To start the operation, it is necessary to operate the operation mode selecting switch 2 as well as the operation switch 3. Further, the fan speed is selected by a separate switch 4. Thus, the procedure which must be followed by the user is complicated and cumbersome.